Like most cancers, myeloma is classified into various groups based on the extent of disease, how fast it is progressing, the type and amount of abnormal protein produced, and the types of symptoms and complications. Staging is important because it helps the specialist determine the optimal timing of treatment, the best type of treatment, and the outlook for remission and survival for each individual with myeloma. The types of plasma cells disorders are as follows:
- Monoclonal gammopathy of undetermined significance, or MGUS: In this condition, a small amount of monoclonal protein is produced, but it does not fulfill criteria for the diagnosis of myeloma. There is no associated anemia, infections, bone disease, or lowering of normal immunoglobulin levels. It is unknown whether this disease will progress. Because MGUS involves no symptoms or complications, it does not require treatment. Instead, the person undergoes regular follow-up and testing so that any progression to malignant disease can be detected early and treated promptly. This type accounts for about 1% of people with plasma cell disorders.
- Smoldering multiple myeloma: This condition involves the findings of abnormal plasma cells that produce a monoclonal protein, but no symptoms or complications of myeloma are present. This condition accounts for about 5% of all cases of myeloma. The disease may remain stable without progressing to active myeloma for years. In some people, it never does. Because the disease is not active, it does not require treatment. Like MGUS, smoldering myeloma requires careful follow-up and testing so that any progression to active myeloma can be detected early and treated promptly.
- Indolent multiple myeloma: People with this type of myeloma have an elevated number of abnormal plasma cells in the bone marrow that may or may not produce monoclonal protein. They also have mild anemia or a few bone lesions, but they have no symptoms. The disease may remain stable for long periods. Treatment begins at the first sign of any disease progression.
- Symptomatic multiple myeloma: This is the full, active form of myeloma. The number of plasma cells in the bone marrow is generally more elevated, with production of monoclonal protein, except in the case of nonsecretory myeloma. Other specific diagnostic criteria must be met before making the diagnosis of myeloma, such as degree of anemia, depression of normal immunoglobulin levels, level of calcium, and presence of bone lesions.
As with all cancers, a system to define the extent of disease, which is important for making treatment decisions and predicting outcomes, has been designated as "staging."
In myeloma, staging has traditionally been based upon the following criteria: level of hemoglobin (RBC level), degree of M protein elevation, serum calcium levels, and the presence of bone lytic lesions. Early stage disease is deemed to be stage I, while extensive disease is deemed stage III. Intermediate findings suggest stage II disease. Recently, a newer International Staging System has proposed the use of serum beta-2 microglobulin and albumin levels to determine stages I to III, suggesting that such markers may more accurately define treatment decisions and, potentially, outcome.
Clarence Sarkodee-Adoo, MD
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